The uses of a lithium ion secondary battery among secondary batteries have been spreading not only as a power source for consumer products such as notebook computers and mobile devices including a cellular phone but also, in recent years, as a power source for driving machines such as an electric vehicle, an electric motor cycle, and a power-assisted bicycle, a power source for small electrically driven machine, and a power source for a power storage system making use of its characteristics such as small and light weight and high energy density.
As a substance capable of desorbing and inserting a lithium ion, a lithium based complex oxide of a transition metal, a carbon material, lithium metal, an alloy based compound, and an oxide carbon material are generally used for a material for positive and negative electrode active materials of a lithium ion secondary battery. Moreover, a carbonate based solvent and a lithium salt as a supporting salt are generally used as a non-aqueous electrolyte.
In a charging and discharging process of the secondary battery, a desorption and insertion reaction of a lithium ion occurs at an interface of an electrode and an electrolyte. However, besides the reaction, an electrolyte solvent or the supporting salt causes a decomposition reaction to form a coating film having a high resistance on the surface of the electrode, which inhibits the desorption and insertion reaction of the lithium ion that primarily should occur. As a result thereof, irreversible lowering of discharging capacity or the like is accelerated, which leads to deterioration of the battery. Therefore, various ideas have been devised to suppress the deterioration.
As one of the ideas, a method for suppressing the decomposition reaction by forming a protective film on the surface of the electrode is included, and the means thereof proposes adding an additive having coating film-forming capability to the electrolyte. Patent Literatures 1 to 3, for example, discloses that when a cyclic monosulfonic acid ester is used as an additive, a coating film is formed on the surface of the electrode to improve battery properties. A proposal to use a cyclic disulfonic acid ester has also been made recently as shown by Patent Literature 4 because the cycle properties and the storage properties (suppression of an increase in resistance and the suppression of lowering in a capacity holding ratio) can be more improved than those for the secondary battery using the cyclic monosulfonic acid ester. As described herein, a sulfonic acid ester-based compound is useful as an electrolyte additive having a coating film-forming capability.